#include <iostream>
using namespace std;
int main()
{
	int n;
	cin >> n;
	int a = 1, b = 1, c;
	for (int i = 2; i <= n; i++)
	{
		c = a + b;
		a = b;
		b = c;
	}
	if (n == 0 || n == 1) cout << n << endl;
	else cout << c << endl;
	return 0;
}